Method of recycling metallic coated scrap pieces

ABSTRACT

A method of recycling metallic coated scrap pieces wherein the coating layer liquidus temperature is lower than the core layer solidus temperature, such as brazing sheet scrap pieces, or metallic coated scrap pieces wherein the upper part of the melting range of the coating layer overlaps the lower part of the melting range of the core layer, by at least partially removing the coating layer from the core layer of the scrap pieces making use of a heat resistant metallurgical vessel having an opening for introducing the scrap pieces into the vessel and an exit for discharging essentially molten alloy. The vessel being rotatable around an axis of rotation. The method including the sequential steps of: filling the vessel with a load of scrap pieces; supplying an amount of energy to the vessel so essentially all the scrap pieces reach a temperature above the solidus temperature of the coating layer; rotating the vessel during and/or after the supplying of the amount of energy for forming essentially molten alloy; removing the essentially molten alloy, having the composition of the scrap pieces&#39; coating layer mixed with small amounts of the core layer, through the vessel exit; and removing the remainder of the load from the vessel.

[0001] The invention relates to a method of recycling metallic coatedscrap pieces, such as brazing sheet scrap pieces, by removing thecoating layer from the core layer of the scrap pieces. The inventionalso relates to the use of a metallurgical vessel for this recyclingmethod.

[0002] Below the invention will be elucidated for brazing sheet scrap,but the method can be used as well for other types of metallic coatinglayers on a metal core.

[0003] During the production of brazing sheet a plate of an aluminiumalloy having a relatively low Si content for the core of the brazingsheet is on one or both sides clad by means of roll bonding with a plateof an aluminium alloy having a high Si content for the clad layer on thecore. This sandwich of core plate and clad plate(s) is subsequentlyrolled so as to bind the clad layer(s) to the core layer and to producethe brazing sheet product having a thickness of typically between 0.2and 3 mm, for use in the production of for instance heat exchangers forautomobiles.

[0004] During the production of the brazing sheet significant amounts ofscrap is produced, for instance the beginnings and ends of the sandwichplates after each hot or cold rolling operation. Because the scrapcontains both aluminium alloys with a high Si content and aluminiumalloys with a low Si content, simple melting of the scrap would resultin an aluminium alloy having a raised Si content as compared to the Sicontent of the core, which is to high to be used for producing similartype core plates, unless diluted with substantial amounts of alloyshaving a very low Si content.

[0005] Various methods are available to separate the clad alloy from thecore alloy in the scrap. One of these methods is described ininternational application no. WO 00/67942. According to this method, theclad layer is separated from the core of the brazing sheet by heatingthe brazing sheet until the clad layer becomes liquid or semi-liquid butthe core remains solid, and removing the clad layer by mechanical meanssuch as a hand held or an automatically operated scraper. This methodhowever is only suitable for individual pieces of about 50-75 mmthickness having a surface area per side of for instance 1 to 5 m²;sheet of about 3 mm is too thin.

[0006] It is an object of the invention to provide an efficient methodof recycling metallic coated scrap pieces, such as brazing sheet scrap,by removing the metallic coating from the core of the scrap pieces.

[0007] It is another object of the invention to provide a method ofrecycling metallic coated scrap such as brazing sheet scrap, with whichlarge amounts of scrap can be recycled.

[0008] It is still another object of the invention to provide a methodof recycling such scrap with which a wide range of sheet thicknesses canbe recycled.

[0009] It is yet another object of the invention to provide a method ofrecycling such scrap that is economical on an industrial scale.

[0010] It is a further object of the invention to provide recycled coreand coating alloys, which can easily be used for the production of newsheet material.

[0011] According to a first aspect of the invention, one or more ofthese objects are reached with a method of recycling metallic coatedscrap pieces of which the liquidus temperature of the coating layer islower than the solidus temperature of the core layer, such as brazingsheet scrap pieces, or metallic coated scrap pieces of which the upperpart of the melting range of the coating layer has an overlap with thelower part of the melting range of the core layer, by at least partiallyremoving the coating layer from the core layer of the scrap piecesmaking use of a heat-resistant metallurgical vessel having an openingfor introducing the scrap pieces into the vessel and exit means fordischarging essentially molten alloy, the vessel being rotatable aroundan axis of rotation, the method comprising the sequential steps of:

[0012] filling the vessel with a load of scrap pieces;

[0013] supplying an amount of energy to the vessel such that essentiallyall the scrap pieces reach a temperature above the solidus temperatureof the coating layer;

[0014] rotating the vessel during and/or after the supplying of theamount of energy for forming essentially molten alloy;

[0015] removing the essentially molten alloy, having the composition ofthe coating layer of the scrap pieces mixed with small amounts of thecore layer, through the exit means of the vessel;

[0016] removing the remainder of the load from the vessel.

[0017] Using this method, a certain amount of energy is introduced for acertain amount of scrap, which amount of energy is just enough to havethe coating layer melted in whole or at least in part. This amount ofenergy should be introduced in a certain limited time period, to preventoxidation, and to minimise diffusion of Si from the coating layer intothe core layer when brazing sheet scrap pieces are recycled. Of coursethe amount of energy has to depend on the percentage of the coatinglayer in the scrap pieces in relation to the total load. It is assumedthat due to the rotation of the vessel, the scrap pieces abrade eachother and thus remove the liquid or semi-liquid coating layer from thecore layer in a fast and efficient manner. It is believed that thecombined effect of temperature and rotation results in a very efficientremoval of the coating layer from the core, without the need foradditional abrading means. It is unavoidable that small amounts of thecore layer will be abraded as well, so the molten alloy will consist fora small part of the core alloy.

[0018] Preferably, an amount of energy is supplied to the vessel suchthat essentially all the scrap pieces reach a temperature above theliquidus temperature of the coating layer. By introducing such an amountof energy, essentially the whole coating layer will melt and be removedfrom the core. Due to the higher temperature it can be expected that themolten alloy will contain higher amounts of the core alloy. Higheramounts of the core alloy could also be present because the liquidustemperature of the coating layer falls into the melting range of thecore layer.

[0019] According to a preferred embodiment of the method, the remainderof the load is removed from the vessel by supplying a second amount ofenergy in the vessel to melt the remainder of the load to form a secondessentially molten alloy, preferably while the vessel is rotated, andremoving the second essentially molten alloy having the composition ofthe core layer of the scrap pieces mixed with the remainder of thecoating layer. When used for brazing sheet scrap, in this way twoseparate streams of essentially molten aluminium alloy are poured out ofthe vessel, a first one with a high Si content mainly originating fromthe clad layer of the brazing sheet scrap, and a second one with arelatively low Si content mainly originating from the core layer of thebrazing sheet scrap. Pouring out the aluminium alloy is an easy way toremove the aluminium alloy from the vessel, and it can be formeddirectly into ingots or piglets. The same holds, mutatis mutandis, forother types of metallic coated scrap.

[0020] Preferably, the inside lining of the vessel has been preheatedbefore the vessel is filled with the load of metallic coated scrappieces, for the recycling of brazing sheet scrap pieces preferably to atemperature of between 550° and 650° C. and more preferred to atemperature of between 6000° and 630° C. In this way the vessel itselfalready can be given the temperature necessary to melt the coatinglayer, and the energy introduced will be used to heat the scrap piecesand to melt the coating layer.

[0021] According to a preferred embodiment the vessel is tiltable andthe vessel is tilted to pour out the essentially molten alloy throughthe opening. The opening of the vessel thus acts as exit means too andno separate exit means are necessary in the vessel.

[0022] Preferably, burning a fuel, preferably natural gas, withsubstantially pure oxygen, generates the energy in the vessel. Byburning a fuel with substantially pure oxygen it is possible to supply asufficient amount of energy in a very fast way, and using natural gasgives a very clean combustion, so the aluminium alloy will not becontaminated by for instance sulphur from liquid fuels.

[0023] According to a preferred embodiment of the method, the vessel isrotated during a time period after the amount of energy has beensupplied and before the first molten alloy is removed. By using anongoing period of rotation after the energy has been supplied, andbefore the first molten alloy is removed, it is assumed that a betterenergy distribution through the brazing sheet scrap is reached,resulting in a better removal of the clad layer from the core layer.

[0024] Preferably, a vessel is used having a useful volume of 3-20 m³,preferably of approximately 5 m³, which is rotated with a velocity of0.2-10 rpm. For a vessel having such a volume, this rotational speedresults in a good mixing and abrading of the brazing sheet scrap pieces.

[0025] It has been found that the method according to the invention canbe used in particular for recycling brazing sheet scrap pieces having acore layer of the AA 6xxx or AA 3xxx type aluminium alloy, such as AA6063, AA 6060, AA 3003, AA 3103 or AA 3005, and a clad layer of the AA4xxx type aluminium alloy, such as AA 4343, AA 4047, AA 4004, or AA4104. For these types, the Si content of the core is up to 0.6% and theSi content of the clad layer is 6.8 to 13%.

[0026] For the brazing sheet types mentioned above, the method accordingto the invention should preferably be used for scrap pieces havingthicknesses of 0.2 to 100 mm, preferably approximately 0.5-15 mm and/orapproximately 40-70 mm. The best results are obtained for thicker scrap,which is scrap having a thickness of about 5-70 mm.

[0027] Preferably the scrap pieces have a square surface area per sideof up to 0.5 m², preferably of 0.01 to 0.25 m²; the pieces thus havingdimensions of approximately 10 to 50 cm. Scrap pieces with thesedimensions mix well in the vessel, whereas too large dimensions maydamage the refractory lining of the vessel during rotation and too smallpieces of scrap will presumably melt in total or stick together withoutan abrading effect.

[0028] According to a preferred embodiment of the method, the vessel ispreheated to a temperature of approximately 620° C., the vessel isfilled with a load of 2 to 5 tons brazing sheet scrap pieces, and anamount of energy of 220-260 kilowatt-hour per ton brazing sheet scrappieces, depending on the type and relative thickness of the clad layer,is supplied in the vessel before aluminium alloy is removed from thevessel. These data can be used for the brazing sheet types as mentionedabove and result in a first amount of molten aluminium alloy having a Sicontent of almost half that of the original clad layer; of course partof the core layer of the scrap pieces is molten as well, especially atthe edges of the scrap pieces. The remainder of the scrap will have a Sicontent that is higher than that of the original core layer, but farlower than a total mixture of clad and core layer. This is of coursebecause it is impossible to remove the clad layer completely from thescrap pieces by melting and rotating.

[0029] Preferably in the above method, the scrap pieces are heatedduring a time period of 20 to 50 minutes, preferably approximately 40minutes. It has been found that a heating period of approximately 40minutes, depending on the load of scrap pieces, is optimal for heatingand removing the clad layer of the scrap pieces. It is not necessary tointroduce an equal amount of energy per minute.

[0030] According to a preferred embodiment of the method, a secondamount of energy of 200-300 kilowatt-hour per ton of the remainder ofthe load is supplied in the vessel to melt the remainder of the load.The amount of energy added must of course be sufficient to melt all theremainder of the scrap; preferably the molten core is overheated forfurther processing in the casthouse without former solidification.

[0031] Preferably, the remainder of the load is heated during a timeperiod of 20 to 40 minutes, preferably approximately 30 minutes. Thisis, depending on the original load, enough time to fully melt the coreof the scrap pieces.

[0032] Optionally fluxing salts are added to the load of brazing sheetscrap pieces when filling the vessel. Such fluxing salts and their useare well known in the art.

[0033] According to a second aspect of the invention, use is made of aheat-resistant vessel having an opening and means for introducing energyinto the vessel, the vessel being rotatable around an axis of rotation,and the vessel being preferably tiltable so as to be able to empty thevessel through the opening, for performing the above described methodfor recycling metallic coated scrap pieces. Such vessels are already inuse for processing aluminium-containing dross at a temperature ofapproximately 850° C. It has been found that such vessels can very wellbe used for performing the method according to the present invention. Aparticular suitable metallurgical vessel is given in European patent EP0 627 014 or U.S. Pat. No. 5,527,380, which documents are incorporatedherein by reference.

[0034] According to a third aspect of the invention, the core alloyand/or clad alloy as recovered from brazing sheet scrap pieces by usingthe method as described above provide an aluminium alloy having acomposition which makes especially the core alloy suitable for use inthe production of new brazing sheet. Moreover, the core alloy and cladalloy are produced in a cost-effective and fast manner.

[0035] The invention also provides a product made from the core alloyand/or clad alloy as recovered by using the method as described above.

[0036] The invention will be illustrated by the following non-limitativeexamples.

EXAMPLE 1

[0037] In an industrial scale experiment, a mixture of pieces of brazingsheet scrap having a thickness of 6.5 mm and 14.5 mm has been used, thescrap pieces having a clad layer on both sides. The pieces had a lengthof approximately 290 mm and a width in the range of approximately 40 to90 mm. The mass of the scrap pieces having a thickness of 6.5 mm wasapproximately equal to the mass of the scrap pieces having a thicknessof 14.5 mm. The core sheet consisted of an aluminium alloy having a Sicontent of 0.1 to 0.19% and the clad layer of an aluminium alloy havinga Si content of 9.54 to 9.94% on both sides of the core. The nominalpercentage of the clad layer was approximately 24% of the total weight,so 12% on each side of the core layer.

[0038] A load of 3295 kg scrap was introduced in an industrial scalemetallurgical vessel as described in European patent 0 627 014, whichwas preheated to a temperature of approximately 620° C. The vessel hadan internal volume of approximately 5 m³. During a time period ofapproximately 33 minutes a total amount of energy of 790 kilowatt-hourwas introduced in the vessel by burning natural gas with substantiallypure oxygen in approximately a 50-50 ratio. During the first 10 minutes,2.2 megawatt was introduced while the vessel rotated at 2 rpm;thereafter during 23 minutes 1.1 megawatt was introduced while thevessel rotated at 0.5 rpm.

[0039] After this treatment a total of 1110 kg aluminium alloy waspoured out having a Si content of 4%.

[0040] Subsequently the remainder of the load in the vessel was heatedwith a total amount of 670 kilowatt-hour during a time period ofapproximately 25 minutes. First during 9 minutes 2.2 megawatt wasintroduced while the vessel rotated with 0.5 rpm. Then during 9 minutes1.43 megawatt was introduced while the vessel rotated at 5 rpm, andduring the last 7 minutes 1.1 megawatt was introduced while the vesselrotated at 0.5 rpm.

[0041] After this treatment 1980 kg aluminium alloy was poured outhaving a Si content of 0.67%.

[0042] Known fluxing salts were added.

EXAMPLE 2

[0043] In an industrial scale experiment, a mixture of pieces of brazingsheet scrap having a thickness of 6.5 mm and 14.5 mm has been used, thescrap pieces having a clad layer on both sides. The pieces had a lengthof approximately 290 mm and a width in the range of approximately 40 to90 mm. The mass of the scrap pieces having a thickness of 6.5 mm wasapproximately equal to the mass of the scrap pieces having a thicknessof 14.5 mm. The core sheet consisted of an aluminium alloy having a Sicontent of 0.1 to 0.19% and the clad layer of an aluminium alloy havinga Si content of 9.54 to 9.94% on both sides of the core. The nominalpercentage of the clad layer was approximately 24% of the total weight,so 12% on each side of the core layer.

[0044] A load of 4140 kg scrap was introduced in an industrial scalemetallurgical vessel as described in European patent 0 627 014, whichwas preheated to a temperature of approximately 620° C. The vessel hadan internal volume of approximately 5 m³. During a time period ofapproximately 43 minutes a total amount of energy of 970 kilowatt-hourwas introduced in the vessel by burning natural gas with oxygen inapproximately a 50-50 ratio. During the first 10 minutes, 2.2 megawattwas introduced while the vessel rotated at 2 rpm; thereafter during 33minutes 1.1 megawatt was introduced while the vessel rotated at 0.5 rpm.

[0045] After this treatment a total of 645 kg aluminium alloy was pouredout having a Si content of 5.3%.

[0046] Subsequently the remainder of the load in the vessel was heatedwith a total amount of 788 kilowatt-hour during a time period ofapproximately 30 minutes. First during 10 minutes 2.2 megawatt wasintroduced while the vessel rotated with 0.5 rpm. Then during 10 minutes1.43 megawatt was introduced while the vessel rotated at 5 rpm, andduring the last 10 minutes 1.1 megawatt was introduced while the vesselrotated at 0.5 rpm.

[0047] After this treatment 3205 kg aluminium alloy was poured outhaving a Si content of 1.1%.

[0048] Known fluxing salts were added.

EXAMPLE 3

[0049] In an industrial scale experiment, brazing sheet scrap pieceshaving a size of approximately 100×300×5 mm, were introduced in a vesselas described in European patent 0 627 014, preheated to a temperature ofapproximately 620° C., in a load of 2580 kg, together with known fluxingsalts. A total amount of 469 kilowatt-hour was introduced.

[0050] During 25 minutes 208 kilowatt-hour pro ton was introduced, whilethe vessel was rotated at 0.5 rpm during 10 minutes, then at 1.0 rpmduring 11 minutes, and at 3.0 rpm during 4 minutes. A first amount of660 kg aluminium alloy was poured out, having a Si content of 4.92%.

[0051] After that during 32 minutes 240 kilowatt-hour pro ton wasintroduced, while the vessel rotated at 0.5 rpm during 10 minutes, at2.0 rpm during the next 10 minutes, and at 5 rpm during the last 12minutes. A second amount of 1860 kg aluminium alloy was poured out,having a Si content of 0.41%.

EXAMPLE 4

[0052] In an industrial scale experiment, brazing sheet scrap pieceshaving a size of approximately 300×300×50 mm were introduced in a vesselas described in European patent 0 627 014, preheated to a temperature ofapproximately 620° C., in a load of 4430 kg, together with known fluxingsalts. A total amount of 1034 kilowatt-hour was introduced.

[0053] During 41 minutes 245 kilowatt-hour pro ton was introduced, whilethe vessel was rotated at 0.5 rpm during all 41 minutes. A first amountof 1500 kg aluminium alloy was poured out, having a Si content of 4.29%.

[0054] After that during 34 minutes 240 kilowatt-hour pro ton wasintroduced, while the vessel rotated at 0.5 rpm during 10 minutes, at 5rpm during the next 10 minutes, and at 0.5 rpm during the last 14minutes. A second amount of 2850 kg aluminium alloy was poured out,having a Si content of 0.52%.

Example 5

[0055] In an industrial scale experiment, a mixture of brazing sheetscrap pieces having a thickness of 0.6 mm and a variable size in theorder of magnitude of 100×300 mm was introduces in a vessel as describedin European patent 0.627 014, preheated to a temperature ofapproximately 620° C., in a load of 1465 kg. All scrap pieces have acore of AA 3xxx (Si content less than 0.62%) and a clad layer of AA 4xxx(Si content of 7.2-12.65%). A total of 273 kilowatt-hour pro ton wasintroduced during 36 minutes while the vessel rotated at 2 rpm. A firstamount of 285 kg aluminium alloy was poured out, having a Si content of2.04%. A second amount of 1045 kg aluminium alloy was; after heating,poured out having a Si content of 1.00%.

[0056] Having now fully described the invention, it will be apparent toone of ordinary skill in the art that many changes and modifications canbe made without departing from the spirit and scope of the invention asherein described.

1. Method of recycling metallic coated scrap pieces of which theliquidus temperature of the a coating layer is lower than the solidustemperature of the a core layer, such as brazing sheet scrap pieces,metallic coated scrap pieces of which the upper part of the meltingrange of the coating layer has an overlap with the lower part of themelting range of the core layer, by at least partially removing thecoating layer from the core layer of said scrap pieces making use of aheat resistant metallurgical vessel having an opening for introducingthe scrap pieces into the vessel and an exit means for dischargingessentially molten alloy, the vessel being rotatable around an axis ofrotation, the method comprising the sequential steps of: filling thevessel with a load of scrap pieces; supplying an amount of energy to thevessel such that essentially all the scrap pieces reach a temperatureabove the solidus temperature of the coating layer; rotating the vesselduring and/or after the supplying of the amount of energy for formingessentially molten alloy; removing the essentially molten alloy, havingthe composition of the coating layer of the scrap pieces mixed withsmall amounts of the core layer, through the exit means of the vessel;removing the remainder of the load from the vessel.
 2. Method accordingto claim 1, in which wherein an amount of energy is supplied to thevessel such that essentially all the scrap pieces reach a temperatureabove the liquidus temperature of the coating layer.
 3. Method accordingto claim 1 or 2, in which wherein the remainder of the load is removedfrom the vessel by supplying a second amount of energy in the vessel tomelt the remainder of the load to form a second essentially moltenalloy, preferably while the vessel is rotated, and removing the secondessentially molten alloy having the composition of the core layer of thescrap pieces mixed with the remainder of the coating layer.
 4. Methodaccording to claims claim 1, 2, or 3 in which wherein the inside liningof the vessel has been preheated before the vessel is filled with theload of metallic coated scrap pieces, for the recycling of brazing sheetscrap pieces preferably to a temperature of between 550° and 650° C. andmore preferred to a temperature of between 600° and 630° C.
 5. Methodaccording to claim 1, wherein any one of the preceding claims, in whichthe vessel is tiltable and the vessel is tilted to pour out theessentially molten alloy through the opening.
 6. Method according toclaim 1, wherein any one of the preceding claims, in which the energy inthe vessel is generated by burning a fuel, preferably natural gas, withsubstantially pure oxygen.
 7. Method according to claim 1, wherein anyone of the preceding claims, in which the vessel is rotated during atime period after the amount of energy has been supplied and before theessentially molten alloy is removed.
 8. Method according to claim 1,wherein any one of the preceding claims, in which a vessel is usedhaving a useful volume of 3-20 m³, preferably of approximately 5 m³,which is rotated with a velocity of 0.2-10 rpm.
 9. Method according toclaim 1, wherein any one of the preceding claims, in which the brazingsheet scrap pieces are recycled having a core layer of the AA 6xxx or AA3xxx type aluminium alloy, such as AA 6063, AA 6060, AA 3003, AA 3103 orAA 3005, and a clad layer of the AA 4xxx type aluminium alloy, such asAA 4343, AA 4047, AA 4004, or AA
 4104. 10. Method according to claim 9,wherein in which the scrap pieces have thicknesses in the range of 0.2to 100 mm , preferably approximately 0.5-15 mm and/or approximately40-70 mm.
 11. Method according to claim 9, wherein or 10, in which thescrap pieces have a square surface area per side of up to 0.5 m²,preferably of 0.01 to 0.25 m².
 12. Method according to claim 9, whereinany one of the claims 9-11, in which the vessel is preheated to atemperature of approximately 620° C., the vessel is filled with a loadof 2 to 5 tons brazing sheet scrap pieces, and an amount of energy of220-260 kilowatt hour per ton brazing sheet scrap pieces, depending onthe type and relative thickness of the clad layer, is supplied in thevessel before aluminium alloy is removed from the vessel.
 13. Methodaccording to claim 12, in which wherein the scrap pieces are heatedduring a time period of 20 to 50 minutes, preferably approximately 40minutes.
 14. Method according to claim 9, wherein any one of the claims9-13, in which a second amount of energy of 200-300 kilowatt-hour perton of the remainder of the load is supplied in the vessel to melt theremainder of the load.
 15. Method according to claim 14, in whichwherein the remainder of the load is heated during a time period of 20to 40 minutes, preferably approximately 30 minutes.
 16. Method accordingto claim 1, wherein any of the preceding claims for the recycling ofbrazing sheet scrap, in which fluxing salts are added to the load ofscrap pieces when filling the vessel.
 17. A method of use Use of aheat-resistant metallurgical vessel having an opening and means forintroducing energy into the vessel, comprising performing the steps ofthe method for recycling metallic coated scrap pieces of claim 1,wherein the vessel being is rotatable around an axis of rotation, andthe vessel being preferably tiltable so as to be able to empty thevessel through the opening, for performing the method for recyclingmetallic coated scrap pieces, such as brazing sheet scrap pieces,according to any one of the preceding claims.
 18. The method of use Useof a heat-resistant metallurgical vessel according to claim 17, whereinthe metallurgical vessel is a dross-recycling converter, in particularas claimed in European patent EP 0 627
 014. 19. Core alloy and/orcoating alloy as recovered from metallic coated scrap pieces such asbrazing sheet scrap pieces by using the method according to any one ofclaims claim 1 to
 16. 20. Product made from the core alloy and/orcoating alloy of claim
 19. 21. The method of claim 1, wherein themetallic coated scrap pieces are selected from the group consisting ofbrazing sheet scrap pieces, or metallic coated scrap pieces of which theupper part of the melting range of the coating layer has an overlap withthe lower part of the melting range of the core layer.
 22. Methodaccording to claim 1, wherein the remainder of the load is removed fromthe vessel by supplying a second amount of energy in the vessel to meltthe remainder of the load to form a second essentially molten alloy,while the vessel is rotated, and removing the second essentially moltenalloy having the composition of the core layer of the scrap pieces mixedwith the remainder of the coating layer.
 23. Method according to claim1, wherein the inside lining of the vessel has been preheated before thevessel is filled with the load of metallic coated scrap pieces, for therecycling of brazing sheet scrap pieces to a temperature of between 550°and 650° C.
 24. Method according to claim 1, wherein the inside liningof the vessel has been preheated before the vessel is filled with theload of metallic coated scrap pieces, for the recycling of brazing sheetscrap pieces to a temperature of between 600° and 630° C.
 25. Methodaccording to claim 1, wherein the energy in the vessel is generated byburning natural gas with substantially pure oxygen.
 26. Method accordingto claim 1, wherein a vessel is used having a useful volume ofapproximately 5 m³ is rotated with a velocity of 0.2-10 rpm.
 27. Methodaccording to claim 1, wherein brazing sheet scrap pieces are recycledhaving a core layer of selected from the group consisting of AA 6063, AA6060, AA 3003, AA 3103 or AA 3005, and a clad layer selected from thegroup consisting of AA 4343, AA 4047, AA 4004, or AA
 4104. 28. Methodaccording to claim 9, wherein the scrap pieces have thicknesses in therange of 0.5-15 mm.
 29. Method according to claim 9, wherein the scrappieces have thicknesses of approximately 40-70 mm.
 30. Method accordingto claim 9, wherein the scrap pieces have a square surface area per sideof 0.01 to 0.25 m².
 31. Method according to claim 12, wherein the scrappieces are heated during a time period of approximately 40 minutes. 32.Method according to claim 14, wherein the remainder of the load isheated during a time period of approximately 30 minutes.
 33. The methodof use of claim 17, wherein vessel is tiltable to be able to empty thevessel through the opening, for performing the method for recyclingmetallic coated scrap pieces.